- From: Marcos Caceres <w3c@marcosc.com>
- Date: Mon, 27 Feb 2012 14:18:55 +0000
- To: Jonas Sicking <jonas@sicking.cc>
- Cc: www-dom@w3.org
(moving to DOM list, from WebApps list...) On Thursday, February 23, 2012 at 3:18 PM, Jonas Sicking wrote: > On Thu, Feb 23, 2012 at 12:21 PM, Marcos Caceres <w3c@marcosc.com (mailto:w3c@marcosc.com)> wrote: > > Hi, > > Would it be possible for DOM4 to define a way for user objects to be able to extend EventTarget (as in Object.create(EventTarget))? > > > > > > > > The use case: give the ability to create objects that can dispatch events using native means… instead of hacking around it like so: > > > > var obj = Object.create(null); > > var dispatcher = document.createElement("x-EventDispatcher"); > > > > //implement EventTarget interface on obj > > Object.defineProperty(obj, "addEventListener", { > > value: function(type, callback, capture){ > > dispatcher.addEventListener(type, callback, capture); > > } > > }); > > > > Object.defineProperty(obj, "removeEventListener", { > > value: function(type, callback, capture){ > > dispatcher.removeEventListener(type, callback, capture); > > } > > }); > > > > Object.defineProperty(obj, "dispatchEvent", { > > value: function(e){ > > dispatcher.dispatchEvent(e); > > } > > }); > > > > > > > > var e = document.createEvent('CustomEvent'); > > e.initEvent("myEvent", false, false, null); > > dispatcher.dispatchEvent(e); > > > > > > > > Also, AFAIK, all JS frameworks have implemented custom ways of handling events and how they are dispatched, so clearly its a desired part of the platform. For example: > > > > http://developer.yahoo.com/yui/docs/YAHOO.util.CustomEvent.html > > http://api.jquery.com/category/events/event-object/ > > http://dojotoolkit.org/reference-guide/quickstart/events.html > > > > Developers have also built their own: > > http://www.nczonline.net/blog/2010/03/09/custom-events-in-javascript/ > > > > Other solutions fire at the document, which means registering listeners on an object that is not the one that needs to receive the event: > > http://tiffanybbrown.com/2011/10/12/dispatching-custom-dom-events/ > > > > So, together with CustomEvents provided by the platform, it would be nice to have a custom EventTarget to fire those things at :) > > I think the way we should do this is to enable instantiating > EventTarget objects using an EventTarget ctor. This won't give you a > neato extension syntax, but I think we'll have to rely on ES.next for > that. Before ecma-script has a better solution you can always > monkeypatch the object. > > So something like: > a = new EventTarget(); > b = new EventTarget(a); // a is the parent in the target chain > > should be doable. I don't know if we need a way to modify the parent > chain after construction. It's somewhat complex to allow this while > still preventing cycles from being created. It would be great to see something like the above.
Received on Monday, 27 February 2012 14:19:31 UTC